The present invention relates to the production of perforated flexible films for packaging products.
International publication WO 02/40250 in the name of the applicant (the “International publication”) discloses a method of perforating polymeric films.
The disclosure in the International publication is incorporated herein by cross-reference.
The disclosure in the International publication is not to be read as a statement of the common general knowledge in Australia or elsewhere.
The International publication discloses a number of different embodiments of tools for perforating polymeric films and a method of perforating films using the tools. The tools comprise a support substrate, for example a roll, and a series of projections extending from the plane of the substrate. The projections are formed so that, in use of the tool in the perforation method, a film of a polymeric material and the projections are brought into contact with each other so that the projections rupture the film and form suitable perforations in the film. The different embodiments of the tools are characterized by different-shaped projections, including (for example) chevron shaped, frusto-conical shaped, and V-shaped projections.
Two common applications for the perforation method, as described in the International publication are:
(a) perforating a polymeric film to change its gas or liquid transfer properties; and
(b) adding a line or area of weakness in a part of a polymeric film to assist the opening or tearing of a package made from the film.
The applicant has carried out further research and development work since lodging the International publication.
The present invention is based on the findings of the further research and development work.